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I. Astronomy of the Earth's Motion in Space

An algebra-based overview of elementary and (mostly) pre-telescope astronomy, for personal study, also for middle school (some), high school (mostly) and beginning college. Starting with the apparent motions of the Sun and stars on the celestial sphere, it explains the seasons of the year, latitude and longitude, time zones and universal time, and the basics of navigation.

Next calendars are described--Julian and Gregorian, Metonic (esp. Jewish), Moslem, Persian and even Maya.

After that the site tells how the spherical shape of the Earth was recognized and measured, leading to the formula for the distance of the horizon, the concept of parallax and the ways the ancient Greeks estimated the distance of the Moon. The Greeks also tried to derive the distance of the Sun, starting the road to heliocentric theory, with roles by Ptolemy, Copernicus, Galileo and Kepler. The section ends with a fairly detailed discussion of Kepler's laws and planetary orbits, which serves as a bridge to the next section, on Newtonian Mechanics.

Interspersed with the above are three web pages on the Moon (which may also be tied to the Greek calculations of the Moon's distance) and one on the precession of the equinoxes, connected to the Milankovitch theory of ice ages.